diff --git a/src/blocks/scratch3_procedures.js b/src/blocks/scratch3_procedures.js
index 645e582ed..3ba743d8b 100644
--- a/src/blocks/scratch3_procedures.js
+++ b/src/blocks/scratch3_procedures.js
@@ -15,8 +15,8 @@ class Scratch3ProcedureBlocks {
         return {
             procedures_definition: this.definition,
             procedures_call: this.call,
-            argument_reporter_string_number: this.param,
-            argument_reporter_boolean: this.param
+            argument_reporter_string_number: this.argumentReporterStringNumber,
+            argument_reporter_boolean: this.argumentReporterBoolean
         };
     }
 
@@ -47,8 +47,19 @@ class Scratch3ProcedureBlocks {
         }
     }
 
-    param (args, util) {
+    argumentReporterStringNumber (args, util) {
         const value = util.getParam(args.VALUE);
+        if (value === null) {
+            return '';
+        }
+        return value;
+    }
+
+    argumentReporterBoolean (args, util) {
+        const value = util.getParam(args.VALUE);
+        if (value === null) {
+            return false;
+        }
         return value;
     }
 }
diff --git a/test/unit/engine_thread.js b/test/unit/engine_thread.js
index 533f72523..15fab7c02 100644
--- a/test/unit/engine_thread.js
+++ b/test/unit/engine_thread.js
@@ -110,7 +110,9 @@ test('PushGetParam', t => {
     th.pushParam('testParam', 'testValue');
     t.strictEquals(th.peekStackFrame().params.testParam, 'testValue');
     t.strictEquals(th.getParam('testParam'), 'testValue');
-    
+    // Params outside of define stack always evaluate to null
+    t.strictEquals(th.getParam('nonExistentParam'), null);
+
     t.end();
 });